Earlier today the WordPress team noticed suspicious commits to several popular plugins (AddThis, WPtouch, and W3 Total Cache) containing cleverly disguised backdoors. We determined the commits were not from the authors, rolled them back, pushed updates to the plugins, and shut down access to the plugin repository while we looked for anything else unsavory.

From my perspective, the responsibilities that a QA team would take on range from monitoring the ticket system, gathering more accurate information for tickets, verifying tickets, and making sure developers are upholding the coding standards, and any other standards, the project is employing, just to name a few.